Microphones convert sounds to electrical signals and are used with a variety of devices where voice communication or voice control is desired. For example, microphones may be used in or with mobile telephones, two-way radios, personal audio devices, computers, and the like. In some cases, the microphone is part of a headset that includes, for example, speakers or other transducers for reproducing sound. In such cases, the speakers within the headset are positioned close to a user's ears. The microphone may be positioned on a boom or arm of the headset which is designed to be located at or near the user's mouth. In other cases, the microphone is not on a boom or arm. Instead the microphone is positioned within the ear canal and is connected to or included within an earphone or ear bud. Such a microphone is referred to as an in-ear microphone or “ear microphone” and eliminates the need for an arm to position the microphone near the user's mouth. An ear microphone receives speech sound from the user's mouth after the sound has propagated through the user's bones and tissue to the ear canal. The ear microphone generates a speech signal which may, for example, be encoded in a first communication device and then transmitted from the first communication device to another or second communication device. The second communication device receives the encoded signal and then decodes that signal. When a speech signal of poor speech quality is encoded at the first communication device, the decoded speech output at the second communication device can be unintelligible. A poor speech signal can be caused by, among other things, improper placement of the ear microphone in the ear canal and reverberations within the ear canal. The speech signal may also be degraded due to the combined effects on the user's voice as it propagates through the several biological media within the body, i.e., the bone and various tissues located between the mouth and the ear canal. Improving the speech signal prior to encoding (at the first communication device) could lead to improved decoded speech output (at the second communication device), which is therefore more intelligible.
Accordingly, there is a need for a method for preprocessing speech for digital audio quality improvement.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.